Conventionally, a port unit queue full response system has been widely adopted as a command control system of a storage apparatus. This port unit queue full response system is a system in which command queues are provided so as to correspond to each port of the storage apparatus, and in which a response (hereinafter called a queue full response) to the effect that queuing is only possible for the host computers connected to ports associated with the command queue is transmitted at the stage where a fixed number of commands or more have accumulated in the command queue.